The present invention relates to an eyeglass lens processing apparatus which performs drilling processing on an eyeglass lens in order to attach a rimless frame.
Generally, drilling (piercing) processing on an eyeglass lens, which is performed in order to attach a rimless frame, such as so-called a two-point frame, is manually performed by a drilling machine or the like. However, recently, an-eyeglass lens processing apparatus which automatically performs the drilling processing is proposed (see U.S. Pat. No. 6,790,124 (JP-A-2003-145328)).
In the automatic drilling processing under numerical control, hole-position data is input. The hole position can be designated with dimensions on a polar coordinate system with, as a reference, a geometric center of a two-dimensional target lens shape (traced outline shape) of the eyeglass lens. However, the hole position is usually designated with dimensions on an orthogonal coordinate system (with an x-axis direction as a horizontal direction and a Y-axis direction as a vertical direction of an eyeglasses) with, as a reference, the geometric center of the two-dimensional target lens shape or with dimensions from a lateral edge of a hole only in the x-axis direction. In any of the methods, the hole-position is designated on a two-dimensional coordinate system.
However, a refractive surface of the eyeglass lens, where to actually form a hole, has a three-dimensional curve, thus raising various inconveniences and contradictions in management of the hole-position data. For example, where to form two holes H1 and H2, side by side, vertically to the refractive surface of the eyeglass lens LE as shown in FIG. 10A, in case processing is made directly with using dimensions xc1 and xc2 of from the geometric center FC of the target lens shape or with using dimensions xh1 and xh2 of from the lateral edge of the holes H1 and H2, then the resulting spacing “da” between two holes H1 and H2, as viewed in a direction along the curve of the refractive surface, deviates from a designated hole spacing “d” under the influence of the curve (inclination) of the refractive surface, thus raising contradiction. This problem becomes conspicuous as the curve increases in the lens refractive surface.